On January 29, the phthalic anhydride market in Shandong experienced volatile consolidation. The mainstream negotiated prices for o-xylene-based phthalic anhydride were 6,100–6,300 yuan/ton, while those for naphthalene-based phthalic anhydride were 5,800–6,100 yuan/ton. The price of raw material o-xylene remained stable, as did the price of industrial naphthalene, leading to steady production costs for phthalic anhydride. Downstream plasticizer prices showed volatile upward movement. Phthalic anhydride production facilities maintained stable operations, with plant operating rates remaining low and steady. The supply of phthalic anhydride in the market tightened. Plasticizer plants maintained stable operating loads, and demand for phthalic anhydride remained firm. The outlook for the phthalic anhydride market points toward continued volatile consolidation.